1. Technical Field
This disclosure relates to an image forming apparatus including a recording head that ejects liquid droplets.
2. Description of the Related Art
Image forming apparatuses (e.g. printers, fax machines, copiers, and multifunction machines having functions of these machines) are known that perform image formation by ejecting liquid (recording liquid) such as ink onto a medium using, for example, a liquid ejection device while transporting the medium. The liquid ejection device comprises a recording head including a liquid ejection head (liquid droplet ejection head) for ejecting droplets of the recording liquid (ink). It is to be noted that the term “medium” as used herein is hereinafter also referred to as a “sheet”, which may be paper or may be made of other materials. The terms “to-be-recorded medium”, “recording medium”, “transfer material”, and “recording sheet”, may be used as synonyms. The terms “recording”, “printing”, and “imaging” may be used as synonyms for the term “image formation”.
The term “image forming apparatus” as used herein indicates an apparatus that forms images by ejecting liquid onto media such as paper, strings, fibers, cloth, leather, metal, plastic, glass, wood, and ceramics. The term “image formation” as used herein indicates not only forming images that have meanings, such as characters and figures, on a medium, but also forming images that do not have meanings, such as patterns, on a medium (i.e., merely ejecting liquid droplets onto a medium). The image forming apparatus may include a textile printing apparatus and an apparatus for printing interconnects. The term “ink” as used herein is not limited to recording liquid, but includes any liquid that can be used for image formation.
One such image forming apparatus, as disclosed in Japanese Patent Laid-Open Publication No. 2006-111002 (Patent Document 1), comprises a recording head configured to eject liquid droplets onto a sheet to form an image; a transport unit configured to intermittently transport the sheet so that the sheet is transported facing the recording head; plural transport rollers disposed downstream the transport unit in a sheet transport direction and configured to transport the sheet in a sheet discharge direction; and plural spurs disposed facing the respective transport rollers and arranged in the sheet transport direction. A guide member is configured to hold the plural spurs and is displaceable between an open position for opening a transport path and a guide position for guiding the sheet. The guide member includes a protection member that is displaceable between a protection position for protecting the spurs and a retracted position retracted from the protection position.
Japanese Patent Laid-Open Publication No. 2007-276220 (Patent Document 2), Japanese Patent Laid-Open Publication No. 2003-175648 (Patent Document 3), and Japanese Patent Laid-Open Publication No. 2006-159664 (Patent Document 4) also disclose image forming apparatuses using spurs.
In the case where a sheet with an image formed is transported while being pressed by a spur, the spur often scratches off the ink on the image formation surface to form a white dotted line. If a sheet is pressed by plural spurs arranged in the sheet transport direction as in the image forming apparatus of Patent Document 1, the resulting white dotted line is more noticeable due to contact with the increased number of spurs.
In the case of reversing a sheet and discharging the reversed sheet into a tray inside the apparatus body, the required transporting force is greater than the transporting force required in the case of discharging the sheet straight ahead, and therefore the image forming apparatus needs to have plural spurs in the sheet transport direction. Such an image forming apparatus tends to form noticeable spur traces.